As a compressor, there exist a 1-cylinder compressor and a 2-cylinders compressor. The 1-cylinder compressor among them has advantages such that a number of components of the compressor is small and that a cost of the compressor is cheap while the 1-cylinder compressor has disadvantage such that vibration of the compressor is greater so that stable operation of the compressor is difficult because the 1-cylinder compressor has greater load torque variation.
Therefore, it is desired that a 1-cylinder compressor is driven with vibration as small as possible, with efficiency as high as possible, and with stability. It is also desired that an arrangement is employed so as to realize performance of an inverter fully, and that the inverter is made with a cost as cheap as possible.
By taking them into consideration, it is proposed from the past that torque controlling is carried out so as to determine speed variation value as great as possible within an extent where decreasing amount in efficiency is suppressed to be equal or less than a predetermined value and vibration does not matter in practice (refer to Japanese Patent Laid-Open Publication No. H10-174488 gazette).
It is also proposed that torque ripple correction amount is decreased following becoming greater of the speed, and that torque ripple correction amount is adjusted corresponding to a peak value of a ripple of a current which flows an inverter (refer to Japanese Patent Laid-Open Publication No. 2001-119981 gazette).